Selfsufficientish.com

1. do I need them?
2. can I get them free?

I have a hardware firewall on the wireless router but on the pc I run avgfree. they dont make a linux version though; possibly 'cos hardly anyone makes linux virusses lol!!!

but still, I prefer to be safe than sorry...

I'm sure there are some anti-virus programs for Linux Mrs F, and I'm sure most of them are free.
BUT, I don't think I would bother, I have run Linux for umpteen years and never come across a virus.
That's not to say there aren't any, but Linux makes it particularly difficult to damage your files remotely as unlike Windows you have to be logged in as root user before you can do anything with files.
Plus the small(ish) community of Linux users compared to Windows users makes it less "interesting" for the hacker/virus writer.

I have a virus scanner on ubuntu. I can only assume I found it on the add/remove list as I'm not clever enough to source programs through Terminal. I installed it to be all clever and to protect my system, used it loads for all of a couple of months, then I got bored with it not finding anything or doing anything clever (Avast had a siren and flashy things!!!) so I don't bother any more. The only problems my 'pootah has can be solved by a good thump on the bottom left hand corner or by turning it upside down and shaking it